Process for the removal of neutral oils from phenolate liquors



Dec. 15, 1964 R. BEMMANN 3,161,688

PROCESS FOR THE REMOVAL OF NEUTRAL. OILS FROM PHENOLATE LIQUORS Filed April 4, 1960 OIL VAPOR STEAM Nu OH SOL.

PHENOL ATE LEQU 0R f STEAM INVENTOR Pad 01f Remove/m ATTORNEYS United States Patent 3,161,688 PROCESS FOR THE REMOVALQF NEUTRAL ()ILS FROM PHENGLATE LIQUORS Rudolf Bemmann, Sandhofer Strasse 106, Mannheim-\Valdhof, Germany Filed Apr. 4, 1960, Ser. No. 19,603 2 Claims. (Cl. 260-627) In the recovery of phenols from phenol-containing oils of varying origin, for example from phenol oil fractions recovered from coal tar; or corresponding fractions from benzine or middle oils resulting from low-temperature carbonization of coal or lignite, furthermore, from phenol oil fractions obtained in the high-pressure hydrogenation of tars and coals, and so on, by means of caustic alkali solutions, particularly sodium hydroxide solution, phenolate liquors are obtained which contain larger or smaller amounts of non-phenolic oils, shortly called neutral oils. These neutral oils have to be removed before commercial products, such as carbolic acid, cresol and xylenol are obtained from the phenolate liquors in conventional grades. As a rule, the removal of neutral oils from phenolate liquors is done by boiling or steaming of the liquors. The process is called clear-steaming of the phenolate liquor. The steaming is preferably done in a continuous process, for instance by passing the phenolate liquor at elevated temperature through a column or tower filled with such bodies as Raschig rings in countercurrent with steam. Due to the hydrolytic splitting of the alkali phenolates, in additionto the neutral oil, a part of the phenols is likewise taken along as distillate with the steam. When the vapors escaping from the clear-.

steaming apparatus are condensed, a neutral oil is obtained which contains more or less phenol; an aqueous condensate also results, which contains some phenol. The quantities of phenol contained in these two products are lost for the recovery of phenol. In order to avoid these losses, it is necessary to free the products of their phenol content in special de-phenolizing plants, whereby additional expenses for materials and labor are incurred.v

It may therefore be stated that there is a requirement for improvement of the conventional clear-steaming process of phenolate liquors in order to avoid, or at least to reduce, the incurred losses in phenol. Such a requirement is most urgently felt when the clear-steaming concerns over-saturated phenolate liquors, since in this case the phenol losses are very considerable and sometimes prohibitive. However, even not over-saturated or nonstaturated phenolate liquors perform unsatisfactorily in the clear-steaming operation, not so much on account of the high phenol losses, as because of the formation of phenol-eontainirlg aqueous condensates which cannot be used without further proctissing, and which must not be allowed to pass into sewers, but which have first to be dephenolized; this is again a cumbersome and expensive operation.

When the phenolate liquors to undergo cleansteaming are alkali-phenolate liq rs, in which the phenols are chemically completely ho to alkali metal, the phenol losses during clear-steaming are comparatively low. However, when so-call over-saturated henolate liquors are treated, considerab larger losses ur. By over-saturated phenolate liquors we understand such phenolate solutions in which the equivalent amount of the phenols present is larger than the equivalent amount of alkali metal present. In industrial processes, it is very important to use over-saturated phenolate liquors in the recovery of phenol, since it is possible to obtain, with a given amount of alkali metal, more phenols than with unsaturated or just saturated phenolate liquors. When 3,161,588 Patented Dec. 15, 1964 an over-saturated phenolate liquor of l20l40% is used, the total amount of the phenols which can be distilled ofi? together with the neutral oils from the phenolate liquor during the clear-steaming process, is about 10% of the total phenols present. When still higher over-saturated phenolate liquors are used, this percentage is even higher. In such cases, the clear-steaming process is uneconomical. It has therefore been proposed to recover neutral oil from over-saturated phenolate liquors not by clear-steaming, but by extraction with selective solvents, for instance parafiinic light benzine. Howeven this proposal has up to now not attained any practical value, since the extraction process is not sufiiciently selective and the recovery of the selective solvent is cumbersome, expensive and leads to high losses, more particularly in view of the fact that considerable amounts of the selective solvent are dissolved in the phenolate liquor.

It is an object of the present invention to provide a. process for recovery of phenols from phenol-containing oils which avoids the above mentioned shortcomings of the above mentioned processes, is simple to perform and can be carried out in inexpensive apparatus.

It is another object to provide a process for the recovery of phenols from phenol-containing oils which permits to make the recovery complete or to keep the loss of phenol at a It is yet another object to provide a process for the recovery of phenols from phenol-containing oils which lends itself with very satisfactory results to the phenol recovery from over-saturated alkali metal phenolates.

Other objects and advantages of the process accord ing to the invention will become apparent from the "fob lowing detailed description.

It has now been found that it is possible completely to avoid the losses of phenol in the clear-steaming of phenolate liquors, or at least to reduce such losses to a negligible quantity, when the phenol-containing vapors erably, hot sodium hydroxide solution is used. This dis- I solves the phenols from the vapors, and condensates are thereby obtained which are practically freeof phenol. The used washing liquor can be combined with the clear steamed phenolate liquor and the so obtained mixed liquor can be passedvon to further processing. Sometimes it may be advantageous to re-use the used washing liquor several times and to return it completely or partly into the washing process. Another way to use the washing liquor is to apply it for the extraction of phenols from phenol-containing oils instead of fresh sodium hydroxide solution.

The washing device may be similar to a washing bottle. However, it is preferable to perform the washing of the vapors with alkali hydroxide in a washing tower, for instance in a column filled with Raschig rings, in which the washing liquor is introduced at the top and meets the ascending vapors in counter-current. A particularly efficient de-phenolization of the vapors is thereby obtained, simultaneously with an enrichment of the washing liquor with phenols. Ihe washing tower can be arranged in series with the clear-steaming apparatus so that the vapors escaping from the latter enter the tower from below. When the clear-steaming apparatus is a continuously operating column-like tower, the washing of the vapors may be effected, according to the invention, in the clear-steaming tower proper; this is a very advantageous embodiment of the invention resulting in a considerably simplified construction of the entire system. In this case it is desirable to provide a special washing zone in the clear-steaming tower, similar to the arrangement shown in the drawing herein.

The accompanying drawing illustrates one embodiment of the apparatus according to the invention in diagrammatic showing.

In the drawing, a tower generally designated by 10 comprises an upper zone 1 aand a lower zone 2, both filled with Raschig rings or similar bodies. The upper zone is a washing zone through which sodium hydroxide solution is introduced into the tower by a line 8. The lower zone is the clear-steaming zone into which phenolate liquor is introduced from the top by a line 9. As the sodium hydroxide solution trickles through the filling bodies in the washing zone I, it meets the neutral oil vapors and reacts with the phenols contained therein by phenolate liquor formation. This liquor joins the phenolate liquor entering at the top of zone 2. In that zone, the combined phenolate liquor is subjected to clear-steaming and collccts at the bottom of the column in a container 6 from where it it continuously drained. Steam is admitted through a pipe 7 to the bottom'of zone 2 and rises in said zone performing the clear-steaming operation. At the top of the tower 10, a mixture of oil vapor and steam escapes through a pipe. 3 leading to a condenser 4 where the mixture of vapors is liquefied. The liquid condensate col lects in a container 5 arranged below condenser 4, and separates into an upper oily and a lower aqueous layer. If the steam admitted through pipe 7 is insufiicicnt, additional steam may be generated by heating the phenolate liquorcollccting in container 6 by a heating device (not shown).

If desired, the. injection of steam through pipe 7 may be dispensed, with and the entire amount of steam required may be generated byheating the phenolate liquor in consolution to the phenolate liquor from the beginning and clear-steam the vapors without washing them.

Exmnple 2 The tests made in Example 1 were repeated with cresolate liquor made by dissolving 97.32 g. (0.9 mole) orthocresol containing a small amount of neutral oil in 400 g. 10% caustic soda solution. g. 10% caustic soda solution were used as washing liquor. After having evaporated 80 cc. water, the washing liquor contained 0.52 g. ortho-cresol, whereas traces of cresol were scarcely detectable in the aqueous distillate, even with very sensitive analytical methods. After separation of small amounts of suspended neutral oil, the distillate was practically'fpure water of condensation. Measurable losses of cresol had not occurred.

In a comparison test, in which the cresolate liquor had been mixed with 20 g. 10% caustic soda solution before tainer 6. In this embodiment of the process the washing liquor is not. collected separately. Therefore, the sodium hydroxide solution has to be so dosaged in consideration of the degree of saturation of the phenolate liquor to be steamed, that no undesired dilution of the phenolate liquortakes place.

Instead of sodium hydroxide solution other caustic solutionsof alkaliametals, for instance, potassium hydroxide solution,.may be used. I i

In the following, the invention will be illustrated by a number of examples.

' Example 1- In 400 g. 10% sodium hydroxide solution (1.0 mole) 112.93 g.'crystalline phenol (1.2 mole) were dissolved which were slightly contaminated by traces of neutral oiL The so obtained phenolate liquor, which is 120% saturated, was heated; in distillation flask to boiling. The resulting va of water, phenol, and neutral oil were passed through aso-called ten bulb-tube filled with 20 g. of 10% hot sodium hydroxide solution of about 100 C., and were then condensed in a Leibig cooler. After about 80 cc. water had escaped fi-om the phenolate liquor, the test was interrupted. sThe washing liquor in the ten bulbtube contained 2.02 g. phenol, whereas in the aqueous distillate only 0.02 g. phenol was found. The washing liquor and the clear-steamed phenolate liquor were combined. The mixture thus obtained contained 112.91 g. phenol. There was a phenol loss of 0.02 g.

In a comparison test, another 20 g. 10% sodium hydroxide solution were added ectly to the phenolate liquor obtained from 112.93 g.' phenol and 400 g. 10% sodium hydroxide solution. The 20 g. sodium hydroxide solution added corresponded exactly to he amount of washing solution used in the preceding test.

80 cc. water were again evaporated. The vapors were, however, not washed with caustic solution, but were condensed directly. The condensate contained 1.69 g. phenol whereas the phenolate liquor had retained 111.24 g. phenol. in this case, the loss of phenol was, therefore, 1.50%. A comparison of the two tests shows that it is more advantageous to wash the vapors from the clearstearning process with a certain amount of sodium hydroxide solution, than to add the same amount of caustic In the clear-steaming of a phenolate liquor which was oversaturated to 113% and which contained in addition to 20% phenols 0.58% neutral oil, a customary steaming column was charged with about 25% of steam. Theneutral oil content of theglear-steamed phenolate liquor amounts to 0.0%. The'oily condensate; contained about 55-60% phenols, whereas the contents in phenols of the, 7 aqueous condensate was betwcn 1 and 2%. The amount I of phenols taken together'was in both about 6 to 7% of the phenols fed in with the phenolate liquor.

However, when the vapors escaping from the. clear-steam ing tower were introduced to the lower portion of the second tower, through which hot 10% caustic soda solution of about'100 C. was streaming down, and when the vapors escaping h'om the second tower were condensed,

' anoily condensate was obtained with less than 10% content in phenols, whereas the aqueous condensate only contained 0.2% phenols. Altogether, the condensates only contained 0.5% of the phenols supplied with the phenolate liquor.

Example 4 When in the apparatus as described in Example 1', a phenolate liquor is processed, which contains in addition to 36% phenols, 0.58% neutral oil and which .is oversaturated at 175%, the test yields, when the washing tower in series arrangement is omitted and the vapors are directly passed to a condenser, an oily condensate with a content in phenols from -75%, while the aqueous condensate contains 2 /2 to 3% phenols. The loss in phenols is 7-8%. When, however, a washing tower containing about 10% caustic soda solution is arranged in series as shown, an oily condensate containing only 5% phenols is obtained, and the contents in phenols of the aqueous condensate is at about 1%. Thus, the loss in phenols in this case is only 0.15 to 0.3%.

Example 5 The clear-steaming of a saturated phenolate liquor with a content in neutral oil of 0.42% yielded a phenol loss of about 6%. Theclear-steaming of the same liquor was then conducted in an apparatus as shown in the drawing. The upper part of the column was charged with 8% sodium hydroxide solution, in an amount of 6 vol. percent calculated on phenolate liquor. The phenol losses in the oily and aqueous condensates were then only about 1%.

It should he understood, of course, that the foregoing disclosure relates only to some preferred embodiments of the invention, and that it is intended to cover all changes and modifications of the embodiments described which do not constitute departures from the spirit of the invention and the scope of the appended claims.

What is claimed is:

1. In a process for the separation of phenols and neutral oils from phenol-containing oils by reacting said oils with an alkali metal hydroxide solution to obtain an alkali metal phenolate solution and subjecting said phenolate solution to a clear-steaming process, the improvement which comprises reacting said oils with an aqueous alkali metal hydroxide solution in a substoichiometric amount in relation to the amount of phenols to be recovered from said oil, so as to obtain an alkali phenolate solution containing from about 110 to about 180% of phenols rela tive to the amount of phenols equivalent to the amount of alkali metal in said solution, subjecting said free phenols containing alkali phenolate solution to said clearnose t3 steaming process by heating it to boiling temperature, washing the phenol-containing vapors escaping from the clear-steaming operation with hot alkali metal hydroxide solution, whereby a liquid phase is obtained which contains alkali metal phenolate substantially free of neutral oils and a vapor phase, which is substantially free of phenols, and recovering said oils by condensation of said vapor phase.

2. The process as claimed in claim 1, wherein the washing step of the phenol-containing vapors escaping from the clear-steaming operation is carried out with hot alkali metal hydroxide solution of 23-10% by weight.

References Cited in the file of this patent UNITED STATES PATENTS Belgium May 19, 1956 

1. IN A PROCESS FOR THE SEPARATION OF PHENOLS AND NEUTRAL OILS FROM PHENOL-CONTAINING OILS BY REACTING SAID OILS WITH AN ALKALI METAL HYDROXIDE SOLUTION TO OBTAIN AN ALKALI METAL PHENOLATE SOLUTION AND SUBJECTING SAID PHENOLATE SOLUTION TO A CLEAR-STEAMING PROCESS, THE IMPROVEMENT WHICH COMPRISES REACTING SAID OILS WITH AN AQUEOUS ALKALI METAL HYDROXIDE SOLUTION IN A SUBTOICHIOMETRIC AMOUNT IN RELATION TO THE AMOUNT OF PHENOLS TO BE RECOVERED FROM SAID OIL, SO AS TO OBTAIN AN ALKALI PHENOLATE SOLUTION CONTAINING FROM ABOUT 110 TO ABOUT 180% OF PHENOLS RELATIVE TO THE AMOUNT OF PHENOLS EQUIVALENT TO THE AMOUNT OF ALKALI METAL IN SAID SOLUTION, SUBJECTING SAID FREE PHENOLS CONTAINING ALKALI PHENOLATE SOLUTION TO SAID CLEARSTEAMING PROCESS BY HEATING IT TO BOILING TEMPERATURE, WASHING THE PHENOL-CONTAINING VAPORS ESCAPING FROM THE CLEAR-STEAMING OPERATION WITH HOT ALKALI METAL HYDROXIDE SOLUTION, WHEREBY A LIQUID PHASE IS OBTAINED WHICH CONTAINS ALKALI METL PHENOLATE SUBSTANTIALLY FREE OF NEUTRAL OILS AND A VAPOR PHASE, WHICH IS SUBSTANTIALLY FREE OF PHENOLS, AND RECOVERING SAID OILS BY CONDENSATION OF SAID VAPOR PHASE. 